This invention pertains to a method of field annealing a thin-film electromagnetic read/write head, and in particular, to such a method producing multi-directional field annealing in such a head.
It is well known that soft magnetic materials contain magnetic-field-responsive structure, such as atomic spins and domains which tend to align with a magnetic field to which they are subjected. When thin-film electromagnetic read/write heads are initially produced, a layer of magnetic material will have, generally speaking, what is known in the trade as an easy access in the plane of the film and a hard axis perpendicular to that plane. However, the particular alignment within the plane on formation of the heads is generally quite random. When such a head is excited to produce flux in the head for reading or writing, this flux field must be strong enough to realign all of the magnetic-field-responsive structure, hereafter simply referred to as domains, with the direction of flux.
Field annealing is a method which has been known for some years. Reference is made in particular to a book entitled Ferromagnetism, by Richard M. Bozorth, D. Van Nostrand Company, 1951, pp. 112ff in which the results of experimentation with field annealing hard magnetic materials with an external field are discussed. Typical techniques involve the application of an external field in which an object to be annealed is placed during an annealing process. Thin-film heads however, have magnetic layers which follow the contour of the head and are not disposed within a single plane. The heads contemplated and discussed in the following description relate to magnetic writing heads of the types disclosed in my prior U.S. patent applications, Ser. No. 170,788, entitled "Magnetic Imaging Apparatus" (filed July 21, 1980), and Ser. No. 472.924, entitled "Differential-Permeability Field-Concentrating Magnetic Read/Write Head" (filed Mar. 7, 1983). These applications describe the construction of a head having concentric poles forming an annular read/write gap and flux-inducing electric coils generally concentrically surrounding the poles when viewed perpendicular to the plane of the head. Flux flowing in an operative head of such construction flows radially toward and away from the poles. Additionally, it flows parallel to and at innumerable angles relative to the general plane of the head. Typical external-field annealing techniques, therefore, would produce domain alignment quite inconsistent with the overall flux path of the head.
It is therefore a general object of this invention to provide a method of field annealing a thin-film magnetic head which overcomes the above-noted problem.
More specifically, it is a desired objective to provide such a method in which multi-directional domain alignment is produced.
It is a further objective to provide such a method for providing domain alignment which corresponds with the operative flux path of a head.
These and additional objects and advantages of the present invention will be more clearly understood from a consideration of the drawings and the following detailed description of a preferred embodiment.